Controlling of odor in the preparation of wood pulp



United States Patent Ofitice 2,839,399 Patented June 17, 1958 CONTROLLING OF ODOR IN THE PREPARATION OF WOOD PULP William M. Qearhart and John B. Thompson, Kingsport, TemL, assignors to Eastman Kodak onipany, Rochester, N. Y., a corporation of New Jersey No Drawing. Application July 29, 1955 Serial No. 525,344

3 Claims. (CI. 92-13) material.

In the pulping of wood particularly by the sulfate or kraft process the odor problem has grams of mercaptan are produced per ton of wood treated in the manufacture of easy bleaching pulp while in kraft operations.

Various methods for diminishing or eliminating odors in such operations have been suggested. For instance, it has been suggested that the relief gases in of Wood be passed through solutions of various metal salts but it has been only the salts of the noble metals which have been found to be particularly effective for this purpose. The passing of relief gases through caustic soda or subjecting them to oxidation to reduce their odor have been suggested but such operations-have undesirable features such as the destruction of certain products therein which are useful commercially. Other methods have involved passing the relief gases through wood or straw. In all of the suggested methods while diminution of the odor in the relief gases may be accomplished the final product contains materials of offensive odor.

One object of our invention is to provide a method for controlling odor in wood cooking operations in which the odor imparting compounds in the relief gases and in the products obtained have been converted to an inoffensive form. Another object of our invention is to provide a method for the control of odor in Wood pulp manufacturein which the relief gases are relatively inoffensive and may be vented directly into the air. A

further object of our invention is to improve not only the odor of the relief gases but also of the products such as turpentine and wood pulp prepared in such operations. A still further object of our invention is to provide for the control of odor in wood cooking operations by the use of aniline or secondary butyl aniline either alone or in admixture with N,N-di-secondary butyl-pphenylenediamine with or Without added peroxide. Other objects of our invention will appear herein.

We have found that in wood pulping operations the formation of materials of offensive odor such as mercaptans or the like is controlled or reduced by adding a Small proportion of aniline or secondary aniline with or the cooking -to 2 lbs. thereof per ton of wood without N,N-di-secondary butyl-p-phenylenediamine to the system in which the wood is cooked. The offensive material is rendered less objectionable as to odor. Our invention is adapted particularly to the attenuation of odor in a sulfate or kraft wood pulping process although it may be used in other chemical wood cooking processes.

We have found that wood pulp operations are rendered less offensive from an odor standpoint if there is incorporated in the system aniline or secondary butyl aniline or a mixture of one of these with N,N-di-secondary butyl-p-phenylenediamine with or without the addition of a peroxide material thereto. Some of the peroxides which. have been found to be particularly useful as an auxiliary to the amines are the alkali metal peroxides such as sodium peroxide, cumene hydroperoxide or the alkyl peroxides such as ditertiary butyl peroxide.

Our invention involves primarily the incorporation of aniline or its admixture with secondary butyl phenylene diamine in the wood cooking system in amounts of 0.5 chips. Below these concentrations the odor is diminished to a less extent while above any additional improvement in diminishing the odor is minor. In those cases, however, where the wood cooked gives greatly increased amounts of mercaptans the use of increased quantities of the odor control agent might be desirable.

We have found that when used with N,N'-di-secondary butyl-p-phenylenediamine, aniline or butyl aniline appears to exert a synergistic effect and the odor reduction obtained is ordinarily superior to that obtained with the secondary butyl phenylenediamine alone. Also we have found when a peroxide is added in the wood cooking operation that ordinarily better odor control is obtained although this may vary from one situation to the next. Our invention includes the use of any amount of peroxide from 0 up to the desired amount but ordinarily convenient proportions of peroxide are 0.25 to 0.5 part thereof per part. of the odor control agent employed.

Although we are primarily interested in the use of the odor control agent in Wood cooking operations, that agent may be employed to control odor in products resulting from the wood cooking operations. For instance, in the pulping of wood there is recovered from the condensed steam from thedigesters a substantial amount of turpentine which may contain, if an odor control agent has not been used, odor producing substances such as methyl mercaptan. The addition of the odor control agent of our invention to the crude turpentine results in vast improvement in odor. As an example odor control agent in accordance with our invention may be added in an amount of 10-50 lbs. per 1000 barrels of turpentine giving vastly improved odor characteristics.

When the aniline or secondary butyl aniline is used in admixture with N,N-di-secondary butylp-phenylenediamine it is desirable that the aniline or butyl aniline make up at least 25% of the mixture. It appears that probably from the standpoint of economy and results that the optimum amounts to be employed for odor control in wood cooking operations is 0.5lb. of each of the butyl phenylenediamine and the aniline or secondary butyl aniline. However, with different species of woods different concentrations may be more effective.

The following examples illustrate the improvement obtained by procedures in accordance with our invention over procedures in which the added to the cooking liquor or the wood cooking system. In each example the white liquor employed contained 41 grams of sodium hydroxide and 14 grams of sodium sulfide per liter. In each case the temperature was held at 320 F. and the pressure at p. s. i. for 2 hours. Although in the examples chips of gum wood are used, our invention is directed to the control of odor with the use odor control agent is not 2 of any of the various types of pulp wood such as pine, spruce, hemlock, fir, birch, maple, poplar, etc. The inhibitors were all blown into the digester with oxygen using a 7 p.'s. i. differential at least 20 minutes prior to release of relief gases therefrom. Theinhibitor cal'cu lations were made on the basis of the bone dry Wood'.

Example 1 1500 grams of gum wood chips were cooked'with 6000 ml. of white liquor. Both the relief gases and the black liquor which resulted from this operation gave forth a very obnoxious odor.

Example 2 Example 3 The operation described in Example 2 was repealed except that .5 lb. of each of the additional materials per ton of bone dry wood chips was added. The improvement in odor was similar to that of Example 2.

Example 4 Example 2 was repeated except that 0.25 lb. of each of the additives wasemployed per ton of bone. dry wood chips. A vast improvement in odor over Example 1 was obtained 'but not as great as that obtained in Examples 2 and 3.

Example 5 1500 grams of gum wood chips were digested. in 6000 ml. of white liquor to which system was added both N,N-di-secondary butyl-p-phenylenediamine and. aniline. in the ratio of 1 lb. of each per ton of bone dry wood chips. The relief gases odor obtained Was similar tothat obtained in Examples 2 and 3.

Example 6 0.5 lb. quantities of N,N'-di-secondary butyl-p-phenylene-diamine and aniline were used per ton of drywood chips. Improvement in odor similar to that of Examples 2, 3 and 5 was obtained.

Example 7 Example 5 was repeated except that 0.25 lb. quantities of each of the additives were employed. Not as much improvement in odor was obtained as with Examples 2, 3, 5 and 6 but the odor was greatly improved over Example 1.

Example 8 Example 5 was repeated except that instead of 1 lb. of aniline, 0.5 lb. quantities of each of secondary butyl aniline and aniline were used per ton of bone dry Wood chips. The odor improvement obtained was comparable to that of Examples 2, 3, 5 and 6.

Example 9 1500 grams of gum wood chips were digested in 6000 ml. of white liquor to which system was added 0.5 lb. of N,N-di-secondary butyl-pfphenylenediamine and. 025 1b. quantities of each of secondary butyl aniline and aniline all on the basis of a ton of bone dry Wood chips. The improvement in odor was comparable to that obtained in Examples 2, 3, 5, 6 and 8.

Example 10 Example 1 1 Example. 5 was repeated but the addition of aniline was omitted. Improvement in odor over Example 1 was obtained but not to the degree obtained with the use of the aniline compound'therein.

Example 12 1500 grams of gum wood chips were digested in 6000 ml. of white liquor to which secondary butyl aniline had been added at the rate of 1 lb. per ton of bone dry Wood chips. The improvement in odor of the relief gases was approximately the same as that obtained in Example 11..

Example 13 Example 12 was repeated except that 0.5 lb. of aniline per ton of bone dry wood chips was used. Similar improvement in odor was obtained.

Example 14 1500 grams of gum wood chips were digested in 6000 ml. of white liquor containing 0.5 lb. of N,N'-di-secondary butyl-p-phenylenediamine, 0.5 lb. of secondary butyl aniline and 1 lb. of sodium peroxide all per ton of 'bone' dry wood chips. The improvement in odor of the relief gases was comparable to that obtained in the better procedures listed in the examples.

We claim:

1. A method for diminishing the odor in the alkaline digestion of wood in which wood chips are cooked with an alkaline liquor which comprises incorporating in the cooking liquor at least 0.5 pound per ton of dry wood of a mixture of N,N-di-secondary butyl-p-phenylenediamine and a material selected from the group consisting of aniline and secondary butyl aniline to substantially diminish the odor in the cooking operation.

2. A method for diminishing the odor in the alkaline digestion of wood in which wood chips are cooked with an alkaline liquor which comprises incorporating'in the cooking liquor at least 0.5 pound per ton of dry wood of amixture of aniline and N,N-di-secondary butyl-pphenylenediamine to diminish the odor in the cooking operation.

3. A method for diminishing the odor in the alkaline digestion of wood in which wood chips are cooked with an alkaline liquor which comprises incorporating in the cooking liquor at least 0.5 pound per ton of dry wood of a mixture of secondary butyl aniline and N,Ndi-secondary butyl-p-phenylenediamine'to diminish the odor in the cooking operation.

References Cited in the file of this patent UNITED STATES PATENTS Remler Jan. 19,1937 

1. A METHOD FOR DIMINISHING THE ODOR IN THE ALKALINE DIGESTION OF WOOD IN WHICH WOOD CHIPS ARE COOKED WITH AN ALKALINE LIQUOR WHICH COMPRISES INCORPORATING IN THE COOKING LIQUOR AT LEAST 0.5 POUND PER TON OF DRY WOOD OF A MIXTURE OF N,N''-DI-SECONDARY BUTYL-P-PHENYLENEDIAMINE AND A MATERIAL SELECTED FROM TEH GROUP CONSISTING OF ANILINE AND SECONDARY BUTYL ANILINE TO SUBSTANTIALLY DIMNISH THE ODOR IN THE COOKING OPERATION. 